From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id EA8316B005D for ; Mon, 3 Aug 2009 10:35:36 -0400 (EDT) Message-ID: <4A76FA08.9090903@redhat.com> Date: Mon, 03 Aug 2009 17:54:00 +0300 From: Izik Eidus MIME-Version: 1.0 Subject: Re: [PATCH 3/12] ksm: pages_unshared and pages_volatile References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Hugh Dickins Cc: Andrea Arcangeli , Rik van Riel , Chris Wright , Nick Piggin , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: Hugh Dickins wrote: > The pages_shared and pages_sharing counts give a good picture of how > successful KSM is at sharing; but no clue to how much wasted work it's > doing to get there. Add pages_unshared (count of unique pages waiting > in the unstable tree, hoping to find a mate) and pages_volatile. > > pages_volatile is harder to define. It includes those pages changing > too fast to get into the unstable tree, but also whatever other edge > conditions prevent a page getting into the trees: a high value may > deserve investigation. Don't try to calculate it from the various > conditions: it's the total of rmap_items less those accounted for. > > Also show full_scans: the number of completed scans of everything > registered in the mm list. > > The locking for all these counts is simply ksm_thread_mutex. > > Signed-off-by: Hugh Dickins > --- > > mm/ksm.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 51 insertions(+), 1 deletion(-) > > --- ksm2/mm/ksm.c 2009-08-02 13:49:43.000000000 +0100 > +++ ksm3/mm/ksm.c 2009-08-02 13:49:51.000000000 +0100 > @@ -155,6 +155,12 @@ static unsigned long ksm_pages_shared; > /* The number of page slots additionally sharing those nodes */ > static unsigned long ksm_pages_sharing; > > +/* The number of nodes in the unstable tree */ > +static unsigned long ksm_pages_unshared; > + > +/* The number of rmap_items in use: to calculate pages_volatile */ > +static unsigned long ksm_rmap_items; > + > /* Limit on the number of unswappable pages used */ > static unsigned long ksm_max_kernel_pages; > > @@ -204,11 +210,17 @@ static void __init ksm_slab_free(void) > > static inline struct rmap_item *alloc_rmap_item(void) > { > - return kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); > + struct rmap_item *rmap_item; > + > + rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); > + if (rmap_item) > + ksm_rmap_items++; > + return rmap_item; > } > > static inline void free_rmap_item(struct rmap_item *rmap_item) > { > + ksm_rmap_items--; > rmap_item->mm = NULL; /* debug safety */ > kmem_cache_free(rmap_item_cache, rmap_item); > } > @@ -419,6 +431,7 @@ static void remove_rmap_item_from_tree(s > BUG_ON(age > 2); > if (!age) > rb_erase(&rmap_item->node, &root_unstable_tree); > + ksm_pages_unshared--; > } > > rmap_item->address &= PAGE_MASK; > @@ -1002,6 +1015,7 @@ static struct rmap_item *unstable_tree_s > rb_link_node(&rmap_item->node, parent, new); > rb_insert_color(&rmap_item->node, &root_unstable_tree); > > + ksm_pages_unshared++; > return NULL; > } > > @@ -1098,6 +1112,8 @@ static void cmp_and_merge_page(struct pa > if (!err) { > rb_erase(&tree_rmap_item->node, &root_unstable_tree); > tree_rmap_item->address &= ~NODE_FLAG; > + ksm_pages_unshared--; > + > /* > * If we fail to insert the page into the stable tree, > * we will have 2 virtual addresses that are pointing > @@ -1481,6 +1497,37 @@ static ssize_t pages_sharing_show(struct > } > KSM_ATTR_RO(pages_sharing); > > +static ssize_t pages_unshared_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + return sprintf(buf, "%lu\n", ksm_pages_unshared); > +} > +KSM_ATTR_RO(pages_unshared); > + > +static ssize_t pages_volatile_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + long ksm_pages_volatile; > + > + ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared > + - ksm_pages_sharing - ksm_pages_unshared; > + /* > + * It was not worth any locking to calculate that statistic, > + * but it might therefore sometimes be negative: conceal that. > + */ > + if (ksm_pages_volatile < 0) > + ksm_pages_volatile = 0; > + return sprintf(buf, "%ld\n", ksm_pages_volatile); ACK. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org